Usually, the final step of manufacturing an electronic device is a testing process. The testing process is used for detecting a defect of the product. One of these testing processes is a burn-in process. In the burn-in process, a lot of electronic devices are operated under a temperature higher than the room temperature for a period of time. It is easier to detect a poor electronic device at a high temperature. The quality of the electronic device passing the burn-in test is better.
The output power signal of the electronic device is measured in the burn-in process. The state of the electronic device is detected by checking the output power signal. The electronic device is in a normal state when the output power signal has a voltage level greater than a predetermined minimal value and the electronic device is in an abnormal state when the output power signal has a voltage level lower than a predetermined minimal value. For example, if the standard power of an electronic device is 5V and the corresponding minimal value is 3.3V, the electronic device is in an abnormal state when the actual output power of the electronic device is smaller than 3.3V.
In the conventional burn-in process, an indicating lamp is connected with the electronic device. When the electronic device is in the normal state, an indicating signal will be generated and then the indicating lamp will be turned on. On the contrary, the lamp will be turned off when the electronic device is in the abnormal state.
The major disadvantage of the conventional burn-in process is that some failed electronic devices may not be found. The output power signal of the electronic device may not be stable when the electronic device is operated. The voltage level of the power signal might be smaller than its minimal value in the first time and larger than the minimal value in the second time. That is, the electronic device might be in the abnormal state during the first burn-in testing period and in the normal state at the next testing period. So, the electronic device having a transient defect will be determined as a good one. The quality of the electronic device will be reduced. Therefore, it is tried by the applicant to solve the above-described problem.